The concept of using spray drying for preparing dry enzyme compositions is known in the art. A protease unhairing enzyme in the form of a whole crude culture of bacteria (Pseudomonas effusa) has been successfully spray dried. A crude culture of Bacillus subtilis to which wood flour was added has also been spray dried. The stability of the activity was poor in the latter case and together with the lack of any cost advantage made spray drying over tray drying impractical. A protease (Bacillus spp.) was spray dried using ultrafilter concentrates but odor, high bacteria count, and hazards related to inhalation of alkaline protease dust made this method of manufacture impractical.
Subsequently attempts were made to develop a process for spray drying enzyme concentrates (primarily from surface culture) obtained by ultrafilter concentration of several culture filtrates. These trials indicated that spray drying of enzymes was possible but activity yields and solids recovery were frequently low, a large amount of product collected on the chamber walls, moisture in the final product was very high, caking and darkening of the dried concentrate was frequently observed and activity retention was poor during storage at room temperature.
Freeze drying has also been utilized to obtain a dry enzyme composition. Initially, freeze drying gave better yields than spray drying. Several of the concentrates still gave problems with freeze drying until it was noted that supplementation of the enzyme concentrates with selected combinations of inorganic salts and insoluble ingredients gave improved results. These findings became the basis of U.S. application Ser. No. 939,745 filed Sept. 9, 1978 by Clifford E. Neubeck assigned to a common assignee U.S. Pat. No. 4,180,917, issued Jan. 1, 1980.
In initial studies, several different formulations of enzyme concentrates were tested in an attempt to select the type and composition of additives to be used in spray drying. These experiments, involved in vacuo drying of bacterial alpha-amylase concentrate to which various salts and insoluble ingredients were added, demonstrated the critical nature of the additives. The variation of the additives had a significant effect on the physical nature, activity recovery, moisture level, lumping, color, etc., of the product. As a result of the above experimentation, initial spray drying experiments were conducted.